Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$144.37	8.124%	$156.0986	$156.10	$156.10	$156.10
Purchase #2	$168.80	12.525%	$189.9422	$189.94	$189.95	$189.90
Purchase #3	$245.32	3.302%	$253.4205	$253.42	$253.40	$253.40
Purchase #4	$153.97	5.680%	$162.7155	$162.72	$162.70	$162.70
Purchase #5	$55.93	7.217%	$59.9665	$59.97	$59.95	$60.00
Purchase #6	$242.76	5.410%	$255.8933	$255.89	$255.90	$255.90
Purchase #7	$44.66	10.155%	$49.1952	$49.20	$49.20	$49.20
7 purchase totals =	$1,055.81		$1,127.2318	$1,127.24	$1,127.20	$1,127.20